Factors influencing the trans-membrane transport of n-octadecane by Pseudomonas sp DG17

In soil bioremediation techniques, the trans-membrane transport of hydrocarbons across the cell membrane is a new and complex point of understanding the process of hydrocarbons biodegradation. In this study, the effect of different environmental factors, including substrate concentration, bacterial inoculums, pH, salinity, substrate analogues and nutrients, on the transport of [C-14]n-octadecane by Pseudomonas sp. DG17 was investigated. The results showed that cellular [C-14]n-octadecane levels increased along with the increase in the substrate concentration. However, the transmembrane transport of [C-14]n-octadecane was a saturable process in the case of equal amounts of inoculum (biomass). The highest concentration of accumulated [C-14]n-octadecane was 0.51 mu mol mg(-1) +/- 0.028 mu mol mg(-1) after incubation for 20 min. Meanwhile, the cellular n-octadecane concentration decreased along with the biomass increase, and reached a stable level. Acidic/alkaline conditions, high salinity, and supplement of substrate analogues could inhibit the transport of [C-14]n-octadecane by Pseudomonas sp. DG17, whereas nitrogen or phosphorus deficiency did not influence this transport. The results suggested that trans-membrane transport of octadecane depends on both the substrate concentration and the microorganism biomass, and extreme environmental conditions could influence the biodegradation ability of microorganisms through inhibiting the transport of extracellular octadecane.